Optical disc having uniform structure

ABSTRACT

An optical disc is manufactured under a uniform condition by forming grooves and lands on the entire surface of the disc. The optical disc is configured to obtain a reliable reproduction signal, and the grooves and lands are formed on a lead-in area, a user data area and a lead-out area of the optical disc. Since the same manufacturing condition can be adopted in mastering discs, the yield can be enhanced and the manufacturing cost can be reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/959,512, filed Dec. 19, 2007, currently pending, which is acontinuation of Ser. No. 11/429,335, filed May 8, 2006, which issued asU.S. Pat. No. 7,376,071, which is a continuation of U.S. patentapplication Ser. No. 10/998,010, filed Nov. 29, 2004, which issued asU.S. Pat. No. 7,164,647, which is a continuation of U.S. patentapplication Ser. No. 10/128,530, filed Apr. 24, 2002, which issued asU.S. Pat. No. 7,065,015, which claims the benefit of Korean ApplicationNos. 2001-61041, filed Sep. 29, 2001 and 2001-23747, filed May 2, 2001,in the Korean Industrial Property Office, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disc which can bemanufactured under uniform conditions by forming grooves and lands onthe entire surface of the disc having a lead-in area, a user data areaand a lead-out area, and which is configured to obtain a highly reliablerecording/reproduced signal.

2. Description of the Related Art

In general, optical discs are widely employed as information recordingmedia for an optical pickup device which records/reproduces informationin a non-contact manner. They are classified into compact discs (CDs)and digital versatile discs (DVDs) according to information recordingcapacity. Furthermore, a DVD disc capable of writing, erasing andreading information can be sub-divided into a digital versatiledisc-random access memory (DVD-RAM) disc and a digital versatiledisc-rewritable (DVD-RW) disc.

FIG. 1 shows a conventional DVD-RAM or DVD-RW disc having a lead-in area10, a user data area 20 and a lead-out area 30. The lead-in area 10contains read only data, such as the disc size, number of track layerson a readable plane or illegal copy preventing information. The userdata area 20 contains user data that can be repeatedly read and/orwritten. The lead-out area 30 contains other disc-related information.

FIG. 1 further shows a partially enlarged view of the lead-in area 10 (aportion A), the user data area 20 (a portion C) and the lead-out area 30(a portion B). In the lead-in area 10 and the lead-out area 30, pits 15are used to record read only data.

In the user data area 20, grooves 23 and lands 25 are alternativelyformed to accommodate recording and/or reproducing information marks 27along a predetermined track. Here, a reference numeral 40 denotes areproduction beam.

A noticeable difference between a DVD-RAM and a DVD-RW is a physicalarea provided for recording. In other words, the DVD-RAM performsrecording on both the lands 25 and the grooves 23, while the DVD-RWperforms recording only on the grooves 23. Application of these twostandard formats results in the following problems.

First, while a DVD-RW having the same physical recording structure as aDVD-ROM (read only disc) has an excellent reproduction compatibility inDVD-ROM drives or DVD players, a DVD-RAM having a phase differencecorresponding to depths of a land and a groove requires hardwaremodification to suitably track lands and grooves. Therefore, aconventional DVD-RAM has a poor reproduction compatibility.

Second, in the context of recording/reproduction characteristics orinjection-molding characteristics in recording data on a groove, thegrooves formed in a DVD-RW are two or more times shallower than that ina DVD-RAM. Here, if necessary, read only data is formed on the lead-inarea 10 in a form of pits 15.

FIG. 2 shows a graph illustrating an amplitude ratio of a reproducedsignal with respect to a pit depth represented in λ/n unit for awavelength (λ) of a reproduced beam to a refractive index (n) of a disc.In cases where the lengths of a recording mark for the minimum recordingmark length T are 3T and 14T, the amplitude ratios denoted by m₁ and m₂are in a range of between 0.2 and 0.3 where the pit depth (correspondingto a groove depth of a DVD-RW) is approximately 0.06 in λ/n unit. Theamplitude ratio is approximately 1 where the pit depth is approximately0.25. Accordingly, the signal level at the pit depth of λ/12n isapproximately 30% (1:0.3) as compared to the case where the pit depth isλ/4n. Therefore, a reliable pit signal cannot be obtained where readonly data as shallow as a groove depth of a DVD-RW is formed in aDVD-RAM.

Third, there is a demand for a multi-layered optical disc having aplurality of recording layers, looking from the direction of an incidentbeam, to enhance the recording capacity. FIG. 3 shows a dual recordinglayer disc having a first recording layer L0 and a second recordinglayer L1. A recording laser passes through the first recording layer L0where a recording is performed on the second recording layer L1. In thiscase, there is a difference in light power between a pit portion and agroove portion. Also, where a physical header representing a basicrecording unit in a data area is used, there is a difference in lighttransmittance because unlike the recording area, the physical headerarea always remains crystallized.

FIG. 4 shows a graph illustrating light power for each of a mirrorportion, pit portion, groove portion and a groove portion with marks. Asshown in FIG. 4, the physical geometry of the first recording layer L0affects the light power.

Table 1 below lists conditions used in the light power experiments.

TABLE 1 Parameter Condition Wavelength (nm) 400 Numerical aperture (NA)0.65/0.85 Minimum mark length (μm) 0.275/0.194 Modulation EFM+(Eight-to-Fourteen Modulation-plus) Track pitch (μm) 0.30, 0.34, 0.38Reflectivity (%) Rc = 25, Ra = 5

In Table 1, Rc represents the reflectivity of a crystallized portion ofa recording layer and Ra represents the reflectivity of an amorphousportion of a recording layer. According to the experimental results, thesmallest decrease in the light power was found in the mirror portion.The light power gradually decreased, in order, with the physicalgeometry of a pit portion, a groove portion and a groove portion withmarks. FIG. 3 shows that a recording/reproducing beam 40 is trapped overa boundary of the lead-in area 10 of the first recording layer L0 andthe data area 20 having grooves. Accordingly, the amount of the lightbeam irradiated onto the second recording layer L1 is different from thecase where a recording/reproducing beam 40 extends over only to thegrooves. Therefore, the groove portion with marks adversely affects therecording power as the data is written on the second recording layer L1of the dual-layered optical disc, resulting in a poorrecording/reproduction efficiency.

Fourth, in order to reduce a spot size of a reproducing beam to attainhigh-density, a numerical aperture (NA) should be increased. However,the problem with a dual recording layer disc is that a difference inlight power becomes more serious as the NA increases. Factors causingthe difference in the light power with increased NA are listed in Table2 below.

TABLE 2 Item Parameter Example Dual recording Structure of firstrecording layer Grooves, pits, etc., layers High NA Number of trackstrapped by beam 85 for NA 0.65 160 for NA 0.85 Incident angle of beam40.5° for NA 0.65 58.2° for NA 0.85

As shown in Table 2, with the grooves and pits formed on the firstrecording layer of a dual recording layer disc, the number of trackstrapped by a beam and the incident beam angle increase as the NA isincreased.

Finally, the manufacturing conditions of the disc mastering may varydepending on different structures of the disc in a lead-in area (pits),a data area (grooves) and a lead-out area (pits). This makes themanufacturing process complex, resulting in a poor yield and anincreased manufacturing cost.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anoptical disc with an improved yield, a reduced manufacturing cost and animproved recording/reproducing capacity, by forming grooves in both alead-in area and a lead-out area so as to have the same manufacturingconditions for discs during mastering.

It is another object of the present invention to provide an optical dischaving an improved structure of multiple recording layers such thatlight power is uniformly irradiated to the multi-layered disc duringrecording/reproducing.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

To achieve the above and other objects of the present invention, thereis provided an optical disc for recording and/or reproduction, whereingrooves and lands are provided to a lead-in area, a user data area and alead-out area of the optical disc.

According to an aspect of the present invention wobbles are formed on atleast one side of the grooves and lands as read only data.

According to another aspect of the present invention, the wobbles in thelead-in area, the user data area and the lead-out area may be modulatedby the same modulation technique or by different modulation techniques.

The wobbles may be modulated by a Quadrature Phase Shift Keying (QPSK)technique or by a Modified Amplitude Modulation (MAM) technique in whicha wobbled portion of a single frequency having a predetermined periodand a non-wobbled portion having a predetermined period are merged.

Alternatively, the wobbles may be modulated by a frequency modulationtechnique, an amplitude modulation technique, a phase modulationtechnique, a minimum shift keying (MSK) modulation technique or a sawtooth wobble (STW) modulation technique.

On the other hand, the wobbles in the user data area may be modulated byat least one selected from a QPSK modulation, a frequency modulation, anamplitude modulation, a MAM modulation, a phase modulation, a MSKmodulation and a STW modulation, and the wobbles in the lead-in area andthe lead-out area are modulated by a modulation technique different fromthat of the wobbles in the user data area.

The optical disc according to the present invention comprises at leastone recording layer.

An optical disc for recording and/or reproduction according to anotherembodiment of the present invention comprises a lead-in area, a userdata area and a lead-out area, wherein each have grooves and landsformed thereon, and data in the user data area is recorded on at leastone side of the lands and grooves.

An optical disc for recording and/or reproduction according to yetanother embodiment of the present invention comprises a lead-in area, auser data area and a lead-out area, wherein each have grooves and landsformed thereon, and the lead-in area further includes a read only dataarea and a write/read data area.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention willbecome more apparent and more readily appreciated from the followingdescription of the preferred embodiment, taken in conjunction with theaccompanying attached drawings in which:

FIG. 1 is a diagram of a conventional optical disc with enlarged viewsillustrating portions A, B and C;

FIG. 2 is a graph illustrating the amplitude ratio of a reproducedsignal with respect to a pit depth;

FIG. 3 is a diagram of a partial cross-sectional view illustrating aconventional optical disc;

FIG. 4 is a graph illustrating light power with respect to a mirrorportion, a pit portion, a groove portion and a groove portion withmarks;

FIG. 5 is a diagram of an optical disc according to an embodiment of thepresent invention with enlarged views illustrating portions D, E and F;

FIG. 6 is a diagram illustrating a one-side wobbling method adopted byan optical disc according to the present invention;

FIG. 7 is a diagram illustrating a wobble-and-land prepit combinationmethod adopted by an optical disc according to the present invention;

FIG. 8A is a diagram of waveforms obtained from wobbles based on afrequency modulation technique adopted by an optical disc according tothe present invention;

FIG. 8B is a diagram of waveforms obtained from wobbles based on a phasemodulation technique adopted by an optical disc according to the presentinvention;

FIG. 8C is a diagram of waveforms obtained from wobbles based on anamplitude modulation technique adopted by an optical disc according tothe present invention;

FIG. 8D is a diagram of waveforms obtained from wobbles based on aModified Amplitude Modulation (MAM) technique adopted by an optical discaccording to the present invention;

FIG. 9 is a diagram of wobbles based on a Quadrature Phase Shift Keying(QPSK) technique adopted by an optical disc according to the presentinvention;

FIG. 10 is a diagram of waveforms obtained from wobbles based on aMinimum Shift Keying (MSK) modulation technique adopted by an opticaldisc according to the present invention;

FIG. 11 is a diagram of waveforms obtained from wobbles based on aSurface Transverse Wave (STW) modulation technique adopted by an opticaldisc according to the present invention;

FIG. 12 is a diagram illustrating wobbles with different track pitchesadopted by an optical disc according to the present invention;

FIG. 13 is a diagram illustrating a lead-in area of an optical discaccording to yet another embodiment of the present invention;

FIG. 14 is a diagram illustrating a header field and a read only datafield of the optical disc of FIG. 13; and

FIG. 15 is a schematic diagram illustrating an example of an opticalrecording/reproducing system which records and/or reproduces data froman optical disc of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 5 shows an optical disc according to an embodiment of the presentinvention. The optical disc includes a lead-in area 100, a user dataarea 120 and a lead-out area 130, and grooves 123 and lands 125 that areformed on the entire surface thereof. User data can be recorded on onlythe grooves 123 or on both the grooves 123 and the lands 125. Where readonly data is recorded, waveforms of wobble signals 105 are consecutivelyrecorded on at least one side of the grooves 123 and lands 125, insteadof pits.

An enlarged view of portions D and E shows that the grooves 123 and thelands 125 are alternately formed in the lead-in and lead-out areas 100and 130, and waveform wobble signals 108 are formed on both the grooves123 and the lands 125. A portion F shows that the grooves 123 and thelands 125 are alternately formed in the user data area 120, and thewobble signals 105 are formed on both the grooves 123 and the lands 125.Recording and/or reproduction are performed while arecording/reproduction beam 110 travels along groove and/or land tracks.

FIG. 6 shows a one-side wobbling method in which wobbles 108′ are formedon at least one side of the lands 125′ and grooves 123′. Alternatively,wobbles may be formed on both sides of the grooves 123′ and lands 125′.

FIG. 7 shows that an optical disc according to another embodiment of thepresent invention may record read only data by a combination of wobbles127 and land prepits 133 formed on lands 125 at predetermined intervals.The land prepits 133 are formed on a predetermined area during themanufacture of a disc substrate. A pickup device provided in arecording/reproducing apparatus (not shown) can easily move to a desiredlocation using the information recorded in the land prepits 133. Also,the pickup device can identify a sector number or type, a land/groove orthe like, and perform a servo control using the information recorded informs of land prepits.

As described above, the optical disc of the present invention has readonly data recorded as wobble signals rather than pits, and the physicalgeometry of the recording layer is the same throughout the entiresurface of the optical disc. Therefore, the optical disc of the presentinvention having multiple layers has less reduction in light power thana conventional optical disc having multiple layers.

FIG. 8A shows an example of a wobble signal modulation adopted by anoptical disc of the present invention. Specifically, a frequencymodulation technique is used, and data is memorized by changingfrequencies of wobble signals 108 and 108′. For example, data isrecorded in combinations of bits of logic “0” or “1”. Data is recordedin such a manner that the frequencies of the wobble signals 108 and 108′are made different in cases of the bits of logic “0” and logic “1”,respectively. For example, the frequency of the wobble signal of thelogic “0” is greater than that of the logic “1”, so as to distinguishthe bits having logic values “0” and “1”.

Alternatively, FIG. 8B shows that a phase modulation technique may beused in recording data, whereby phases of wobble signals 108 and 108′are shifted. That is, data is recorded in such a manner that the phasesof the wobble signals in cases of bits of logic “0” and bits of logic“1” are made different. For example, a phase difference of 180° is madebetween the wobble signal of the logic “0” and the wobble signal of thelogic “1”.

FIG. 8C shows that wobble signals can also be modulated by an amplitudemodulation technique. That is, data is recorded in such a manner thatamplitudes of wobble signals of bits of logic “0” and “1” are madedifferent.

FIG. 8D shows that data may be recorded by a Modified AmplitudeModulation (MAM) technique, in which a wobbled portion 135 of a singlefrequency having a predetermined period and/or a non-wobbled portion 137having a predetermined period, are merged. For example, the lengths ofneighboring wobbled portions or the lengths of neighboring non-wobbledportions are made different, thereby recording data.

In addition, FIG. 9 shows that data can be recorded by a QuadraturePhase Shift Keying (QPSK) modulation, whereby the phases of therespective wobble signals 140 are different from each other at 90°.Here, a reference numeral 145 denotes a recording mark corresponding touser data. As described above, where read only data is recorded aswobble signals, both the user data and the read only data are stored inthe groove and/or land tracks, thereby enhancing the utilizationefficiency of a recording area of a disc.

FIG. 10 shows that data can be recorded by a Minimum Shift Keying (MSK)modulation, whereby only the frequencies in a predetermined periodcomprising consecutive wobble signals 140 are varied.

FIG. 11 shows that a saw tooth wobble (STW) modulation may be employed,whereby saw tooth wobbles 150 are formed. The logic states “0” or “1” ofthe saw tooth wobbles 150 are determined by the shapes of a relativelysharply sloping portion 150 a and a relatively gently sloping portion150 b.

FIG. 12 shows that a crosstalk between tracks can be reduced by makingtrack pitches TP1 and TP2 of wobbles different.

FIG. 13 shows a lead-in area of an optical disc according to yet anotherembodiment of the present invention. That is, a read only data area 103and a write/read data area 105 are provided in the lead-in area (i.e.,100 shown in FIG. 5) of the optical disc. In the read only data area103, data is recorded by first wobbles. In the write/read data area 105,second wobbles are formed. The first and second wobbles may be modulatedby different modulation techniques or indicated by differentspecifications. In other words, the first wobbles are modulated by atleast one selected from a QPSK modulation, a frequency modulation, anamplitude modulation, a phase modulation a MAM modulation, a MSKmodulation and an STW modulation, and the second wobbles are modulatedby a modulation technique different from that for the first wobbles.

FIG. 14, with reference to FIG. 13, shows an example of a header field101 and a read only data field 102 of the optical disc shown in FIG. 13.That is, address information is contained in the entire area of thegrooves in the write/read area 105, and the header field 101, indicatingthe address information, and the read only data field 102 are providedin the read only data area 103. The header field 101 may be positionedat the front or rear of an error correction code (ECC) recording unit orat the interface of ECC recording units. Here, the specification ofwobbles in the header field 101 may be identical with or different fromthat of wobbles in the write/read data area 105 or read only data area103. In particular, as shown in FIG. 13, wobbles formed in the read onlydata field 102 of the read only data area 103 are high-frequency wobblesand wobbles formed in the header field 101 and the write/read data area105 are low-frequency wobbles. This arrangement prevents a reproductionsignal from deteriorating as the address information contained in theheader field 101 is recorded at high frequency. Also, to reduce thecrosstalk between the tracks, track pitches from the write/read dataarea 105 and the read only data area 103 may be set differently fromeach other. For example, the track pitch for the read only data area 103may be greater than that of the write/read data area 105.

The optical disc of the present invention may further include apredetermined area formed for a specific purpose in addition to thelead-in area 100, the data area 120 and the lead-out area 130. Forexample, the predetermined area may be a burst cutting area (BCA) forcopy protection.

FIG. 15 is a schematic diagram illustrating an example of an opticaldisc recording/reproducing system which records and/or reproduces datafrom an optical disc of the present invention. The system includes alaser diode 150 which radiates light, a collimating lens 152 whichcollimates the light radiated from the laser diode 150, a polarizingbeam splitter 154 which changes the traveling path of incident lightaccording to the polarization direction of the incident light, a ¼wavelength plate 156 and an objective lens 158 which focuses theincident light onto an optical disc 160. The light reflected from theoptical disc 160 is reflected by the polarizing beam splitter 154 andreceived by a photodetector, e.g., a quadrant photodetector 162. Thelight received in the quadrant photodetector 162 is converted into anelectrical signal and output to a channel 1, in which the electricalsignal is detected as an RF signal, and to a channel 2, in which theelectrical signal is detected as a wobble signal by a push-pull method.Here, H1, H2, H3 and H4 denote DC amplifiers, and Ia, Ib, Ic and Iddenote first through fourth current signals output from the quadrantphotodetector 162.

According to an optical disc of the present invention, read only datacan be formed by various modulation schemes described above. Inparticular, wobble signals can be formed on the lead-in area 100, thelead-out area 130 and the user data area 120 by the same modulationtechnique.

On the other hand, wobbles can be formed by different modulationtechniques according to the disc area, that is, the lead-in area 100,the user data area 120 or the lead-out area 130. For example, at leastone selected from a frequency modulation, a phase modulation, anamplitude modulation, a MAM modulation, a QPSK modulation, a MSKmodulation and an STW modulation can be employed in the user data area120. Then, a modulation technique different from that employed in theuser data area 120, may be employed in the lead-in area 100 and thelead-out area 130.

To increase the storage capacity, the present invention provides a dischaving at least one recording layer. For example, a dual recording-layerdisc of the present invention comprises grooves and lands which areformed on the entire surface of the dual recording-layer disc, and readonly data which is formed uniformly as wobble signals. Thus, there is nodifference in the light power at the boundary between the lead-in areaor lead-out area and the user data area. Furthermore, efficiency of arecording area is enhanced because the read only data is recorded aswobble signals, allowing both the user data and the read only data to bestored in the groove and/or land tracks.

In the optical disc according to the present invention, grooves areconsecutively formed throughout the entire surface of the disc, whicheases the manufacturability and provides advantages from the viewpointof controllability of mastering parameters. Also, since the samemanufacturing condition can be adopted in mastering discs, the yield canbe enhanced and the manufacturing cost can be reduced. Furthermore, thelight power can be uniformly adjusted while recording/reproducing dataon/from a multiple-layered disc, by forming read only data as wobblesrather than pits.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A method of reproducing data with respect to an optical storagemedium comprising a lead-in area, which comprises a first area having afirst track pitch and a second area having a second track pitch, a dataarea, and a lead-out area, the method comprising: reproducing data withrespect to one of the first and second areas which has a greater trackpitch than a track pitch of the other one of the first and second areas;and reproducing data with respect to the data area.